Line-Of-Sight, LOS, multiple-input multiple-output, MIMO, is a technology with potential to drastically increase throughput in point-to-point radio communication links, e.g., microwave radio links used in a backhaul network.
A radio link with LOS-MIMO technology exploits multiple transmit and multiple receive antennas in order to increase data throughput in a point-to point communication link. By using more than one transmit and more than one receive antenna, the technology enables the simultaneous transmission of several parallel data streams over spatially multiplexed radio links super-imposed on the point-to point communication link. This is in contrast to a conventional radio link with a single transmit and a single receive antenna, where only one data stream can be transmitted over the hop at any given time.
Most radio link communication networks, and microwave frequency radio link communication networks in particular, henceforth referred to as ‘radio networks’ need to be planned before being deployed. Planning of a radio network is done, e.g., in order to ensure that individual radio links do not suffer extensive interference from each other, and also to ensure that radio links can expect a sufficient signal to noise ratio, SNR. However, perhaps most importantly, radio link planning is done in order to give estimates of radio link availability, i.e., estimates of link down-time. This is done in order to ensure that operator demands on availability are met, as customer satisfaction with the network is to a large extent dependent on network outage and down-time.
A crucial component in radio planning is a planning tool which comprises models of how radio links are expected to behave given certain radio link operating conditions such as link distance, rain intensity, etc. Such models are then used by the tool in order to give a user of the tool a prediction of radio network performance, often comprising availability, given a set of input parameters.
The International Telecommunications Union, ITU, and others, have developed extensive models of link availability and also radio network planning tools for user support in the deployment of radio link networks based on single-input single-output, SISO, radio links and cross-polar interference cancellation, XPIC, radio links. Such models are readily available in the prior art.
The ITU and others have also developed statistical models for the behavior of SISO propagation gain, i.e., statistical models of received signal power given transmitted signal power. These models are readily available in the prior art will henceforth be referred to as SISO attenuation models. See, e.g., ITU-R P.530-14 “Propagation data and prediction methods required for the design of terrestrial line-of-sight systems”, and ITU-T G.827 “Availability performance parameters and objectives for end-to-end international constant bit-rate digital paths”.
In some SISO attenuation models, the refractivity gradient and the geoclimatic factor (K factor) constitute required input parameters. Such parameters are available from databases which are indexed by the radio link location. Thus, given the geographic location of a future radio link deployment, data on, e.g., refractivity gradient and the geoclimatic factor can be obtained.
However, the models and tools discussed above do not cover the availability and outage estimation of LOS-MIMO radio links.
Hence, there is a need for a method to model LOS-MIMO link availability, and also a network planning tool with support for LOS-MIMO radio links.